Nickel etch composition

ABSTRACT

A METHOD IS PROVIDED FOR IMPARTING DECORATIVE, LIGHT DIFFUSING AND/OR NON-REFLECTIVE ETCHING TO NICKEL SURFACES WHICH INCLUDES IMMERSING OBJECTS HAVING CLEAN NICKEL SURFACES IN A SOLUTION HAVING A PH WITHHIN THE RANFE OF 9-12 AND CONTAINING A NICKEL OXIDANT, ETHYLENEDIAMINE AND A SOURCE OF SULFATE ION, FOR A PERIOD OF TIME SUFFICIENT TO FORM CRYSTALS ON THE NICKEL SURFACES, WITHDRAWING THE OBJECTS WITH THE CRYSTAL FORMATION THEREON FROM THE NICKEL TION, REMOVING ANY REMAINING SOLUTION FROM THE NICKEL SURFACES, AND IMMERSING THE OBJECTS IN A CRYSTAL SOLVENT TO DISSOLVE THE CRYSTALS, AND REMOVING THE OBJECTS WITH THE ETCHED NICKEL SURFACES THEREON, THE PATTERN OF THE ETCHING BEING SUBSTANTIALLY THE SAME AS THE ORIGINAL CRYSTAL FORMATION THEREON, FURTHER, SOLUTIONS ARE PROVIDED FOR IMPARTING THE DECORATIVE, LIGHT DIFFUSING AND/OR NON-REFLECTIVE ETCH AND OBJECTS HAVING DISPOSED THEREON DECORATIVE, LIGHT DIFFUSING AND/OR NON-REFLECTIVE ETCHED NICKEL SURFACES.

United Sta Petnf Q 3,804,768 Patented Apr. 16, 1974 NICKEL ETCHCOMPOSITION Frederick Walter Eppensteiner, Southfield, Mich assignor toM & T Chemicals Inc., New York, N.Y.

No Drawing. Original application Mar. 26, 1969, Ser. No. 810,824, nowPatent No. 3,669,776. Divided and-"this application Dec. 2, 1970, Ser.No. 94,634 1 Int. Cl. C09k 3/00 US. Cl. 252--79.4 j s ABSTRACT OF THEnrsc osUnE A method is provided for imparting decorative, lightdiffusing and/or non-reflective etching to nickel surfaces whichincludes immersing objects having clean nickel surfaces in a solutionhaving a pH within the range of 9 -12 v and containing a nickel oxidant,v etl ylenediamine and a source of sulfate ion, vfor aperiod of timesufficient to form crystals on the nickelsurfaces, withdrawing theobjects with the crystal formation thereon from the, solution, removingany remaining solution from the nickel surfaces, and immersing theobjects in a crystal solvent to dissolve the crystals, and removing theobjects with the etched nickel surfaces thereon, the pattern'of theetching being substantially the same as the original crystal formationthereon. Further, solutions'are provided for imparting the decorative,light diffusing and/or non-reflective etch and objects having disposedthereon decorative,light diffusing and/or non-reflective etched nickelsurfaces.

This application is a division of copending application Ser. No.810,824, filed Mar. 26, .1969, now US. Pat. 3,669,776. H

Generally speaking, this invention relates to a method for imparting atextured, decorative, non-reflective and/or light diffusing surface toobjects having nickel. surfaces. More particularly, this inventionrelates totmethods for imparting such etched and/or decorativeand-non-refiective surfaces to objects having nickel surfaces whileavoiding any damage to the advantageous properties of the nickel plateitself. 7 1

With the ever increasing use of nickel, surface in.-.all phases of oureconomy, there is-a corresponding concern with regard to its use inconjunction withareaswhere light diffusing and/or non-reflectivesurfacesare most the labor involved is extremely high, relatively speaking.Whenone considers mass produced nickel plated articles which may beincorporated in such articles as automobiles, the cost of mechanicallyetching some such objects becomes extremely prohibitive economically Asis well understood, there is a plurality of chemical processes known inthe art for chemically stripping nickel plate from base metal articles.However, the processes are directed mainly to'removing imperfect platedsurfaces which for one reason or another were not properly plated in thefirst place and because of the relative value of the base "metal articleto which the nickel plate has been affixed, it is economically feasibleto remove the imperfect plated surfaces for replating them with properlyplated surfaces. However, since these processes are directed to removalof substantially all of the nickel plate from the base metal articles,they are not satisfactory for removing only small portions of the nickelplate in a serrated, textured or etchedpattern for providing a finaldecorative, light diffusing and/or non-reflective nickel surface.

Thus, the problem arises where in order to impart decorative and/ornon-reflective'etching to nickel plated surfaces, mechanical means mustbe used for removing only a small part of the actual nickel plate whileat the same appropriate and/or desirable such as in areas where theHowever, as is well known, nickel surfaces are general 1y shiny innature. If it is attemptedto impart an etched or textured lightdiffusing surface to objects having nickel surfaces by mechanical means.suchas grinding and/or time not causing any substantial change to theplated surfaces to the extent where the plate would no longer providethe enhanced protective coating for the base metal article to which theplate has been aflixed in the first place. The further use of mechanicalmeans for solid nickel objects may be effective for certainapplications, but such mechanical processes may be economicallyprohibitive for mass production operations in which many thousands ofthe same type article may be produced in a single production run.

' -On the other hand, those chemical processes known in the prior artwhich may provide economically satisfactory operations have provedunsatisfactory in that no substantial control can be made of the nickelremoval so as to produce only a textured and/ or non-reflective nickelplated surface as a'final product, but rather remove unsatisfactorilylarge amounts of the nickel plate from the base metal article.

-By contrast, and quite unexpectedly, it has now been found inaccordance with this invention, a method for imparting a-decorative,light diffusing, and/or non-reflective etching to nickel surfaces in atwo-step process which requires the formation of first a crystallinecoating on nickel-surfaced objects in a chemical bath, with thesubsequent'removal of the coating in a solvent bath to produce an etchedpattern. The first step is accomplished by forming a nickelethylenediamine sulfate crystal on the work in situ. This is achieved byusing a nickel oxidant in combination with ethylene diamine and sulfateion. Objects having clean nickel surfaces are immersed in a solutionhaving a specific pH range and containing a nickel oxidant,ethylenediamine and a source of sulfate ion for a period of timesufficient to form the crystals of nickel ethylenemechanical needleetching, certain difficulties may arise in that there may betooldeepor.unevenetch so as to remove too much of the nickel fromsurfaces platedwith nickel. With such an arrangement, theremaylbedamageto the actual plate itself,;thus reducing theadvantages diamine sulfate,withdrawing the objects with the crystal formationthereon from thesolution, removing any remaining solution from the nickel surfaces, andimmersing the objects in a solvent to dissolve the crystals.

With such an arrangement, nickel-surfaced objects are achievedhaving theappropriate and desirable etched pattern thereon with the etched patternbeing substantially the same as the original crystal formation which wasformulatedin a solution noted above and with removal of the originalplate on those objects avoiding substantial change in the propertiesthereof, and further, most importantly, without any substantial effecton the nickel plate in its protective role as covering the original basemetal article. It should be understood, however, that allowingnickel-plated objects to be immersed in the etching soluaccordanceherewith, may cause damage to those objects merely because the depth ofthe etch may proceed clear through the plate. If plated objects are tobe etched in accordance herewith, it is a simple matter to calculate thedepth of the etch desired and then to select a plate depth of sufficientwidth to accommodate the etch desired withou sacrificing any of theprotective qualities of the plate on the base metal.

Accordingly, it is one object of this invention to produce decorative,light diffusing, and/or nonrefiectiv'e nickel surfaced objects whichhave disposed in the surfaces there'- of an appropriate textured and/oretched pattern. It is a further object of this invention to provide amethod for imparting decorative, light diffusing, and/ or non-reflectiveetching to nickel-plated surfaces in the absence of substantial changein the properties of the nickelcoating in the first place. i It is astill further object of this invention to produce chemical solutionswhich are capable of imparting satisfactory etched nickel surfaces, andfinally, it'is an object of this invention to produce such satisfactoryetched, textured, light diffusing, and/ or non-reflectivenickel-surfaced objects by a method which is economically appropriatefor mass production techniques.

With the foregoing and additional objects in view, this invention willbe described in more detail and other, ob.- jects and advantages will beapparent from the following description and the appended claims. i v

Before describing this invention in more detail, it may be well to notethat this invention has been found applicable to a wide variety ofnickel-surfaced objects having a plurality of different configurationssimply because the etching achieved in accordance herewith is done in achemical manner by immersing the objects in solution so that howeverintricate the configuration of the object in the first place it can besatisfactorily etched and/or ,textured over the entire surface thereofor those surfaces upon which such texture and/or etched pattern isdesired.

For example, satisfactory results have been achieved in accordanceherewith, and under satisfactorily and economically attractiveconditions on commercial scale operations with chemical solutions formedby admixing ethylenediamine within the range of -250 ml./l., anyconvenient source of sulfate ion including the alkali metal sulfates andbisulfates, sulfuric acid, ammonium sulfate and ammonium bisulfatewithin the range of between about 10-145 g./l. of sulfate ion, andanyconvenient form of nickel oxidant including chemical oxidants such asnitro aromatic compounds like alkali metal salts, sodium nitrobenzoate,sodiumnitrophenolate, 0-, m-,- pnitrobenzoic acid and mixtures thereof,0-,' m-, p-nitro; benzene sulfonic acids and mixtures thereof,'o-, m-,pnitrophenols and mixtures thereof, nitroparafiins such-as nitropropane,inorganic oxidants such as sodium vandpotassium bromates, iodates andperiodates, and ammonium persulfate.

These chemical oxidants are admixed in the solution in the range ofbetween about -3-g./l. to the upperlimit of solubility depending upontemperature and the concentration of the other ingredients. It is to beunderstood, however, that electrolytic oxidation is a convenient andsatis-' factory source of nickel oxidation in accordance herewith,depending upon the circumstances and the conditions of operation. I

The nickel-surfaced objects are then immersed in the solution for aperiod of time sufficient to formthe nickel ethylenediamine sulfatecrystals thereon, removing the tion: The r'es'filting'product hasdisposed thereon a decorative etched pattern with the etching beingsubstantially the same as the previous crystal formation and with littleremoval of the nickel and/or little removal of protective nickel platefrom base metal articles so plated.

In considering generally the conditions for achieving the most enhancedresults in connection herewith, which conditions are more specificallyset forth below, one may note thatsatisfactory etched surfaces areachieved in accordance herewith when the crystal forming solution ismaintained at a temperature within the range of between about ambient to99 C. (or boiling) and a pH within the range of between about .9-12.

It has been found that the most satisfactory results are achieved inaccordance herewith if the nickel-surfaced objects'to be etched arefirst thoroughly cleaned probably because soil impurities and oxideswhich may accumulate on old nickel plated surfaces may interfere withthe proper chemical interaction in the etching solution. Therefore, ithas been found especially preferred that the etching achieved inaccordance herewith be applied to newly plated nickel surfaces, althoughit is to be understood that satisfactoryresul ts are achieved as long asthe plated surfaces have been appropriately cleaned and activated priorto immersion of the plated objects in the etching solution.

Accordingly, it has been found that satisfactory results are achieved inaccordance herewith in a typical fiow pattern including, for example,first taking a clean steel panel,

applying, as well known, nickel plate to the steel panel for 20 minutesat 60 a.s.f. (amperes per square foot), rinsing the panel with clearwater, immersing the panel in an etching solution in accordance herewithfor 10 minutes, removing the etched panel from the etching solution andrinsing with clear water, immersing the panel in a solvent for thirtyseconds, immersing the panel in a cold water rinse and then a hot waterrinse and then drying. It should be understood, further,.that etchedplated objects producedin accordance herewith may be further processedwithichromium and/or other electroplates as desired and as well'known inthe art of nickel plating generally.

A preferred cycle of operation in accordance herewith for formulatingthe particular etched and/ or non-reflective concentration of'the otheringredients, and preferably 25 g./l. of p-nitrobe'nozic acid. As analternative oxidant of equal value in practicing the preferred cycle inaccordance here'v'vith,'potassium iodate is used as providingsatisfactoryujesults and generally in the range noted for p-nitrobenzoicacid, and with a preferred range of 3 g./l. to saturatio'nL Theadmixture is maintained at a temperature between ab'outambient-to 99 C.,and preferably C.

The pH of the etching solution is within the range of 9-12,

and-preferably "10.5. Thereafter, newly plated nickelsurfaeed object'sand/or thoroughly cleaned nickels'urfaced"'objects are immersed in theetching solution for a period of 'timefof between about 5 minutes and 2'hours depending upon various factors including the A degree of etchdesired and the age of the etching solutiofn', andu'sually' for about 15minutes.

objects from the crystal-forming solution, and removingAcrystallinepattern is produced over the entire surface of' thenickel-surfaced objects immersed in the etching'solution and thereafterthe objects are removed from the'etching solution and rinsed with coldwater. Thereafter,"the"objects are immersed in any crystal-dissolvingsolution','-and preferably a 50% hydrochloric acid pickle, and remain inthe solution for a period of time necessary to dis'solve' the crystalsthereon, and preferably for about thirty seconds-in order to dissolvethe crystal formation.

Thereafter, the objects are removed from the dissolving solution andwashed'first with cold water and then with hot water andv then dried.The nickel-surfaced objects have formed thereon an etched and/ortextured pattern over the entire surface thereof withthe formation ofthe pattern being the same as the original crystalline formation on theobjects as they were removed from the etching solution.

It is to be understood that the novel etching solutions produced inaccordance herewith have a satisfactory etching life. 'It has been foundthat satisfactory results are achieved with the solutions formulated inaccordance herewith over an extended period of time. However, it hasbeen found that after an extended period of time, the crystallineformation becomes much slower and longer immersion times have providedsatisfactory results up to and including two hours. In this connection,it has been found that the pH range of between about 9-12 is mostsatisfactory with a pH range much above 12 not producing assatisfactorily etched surfaces. However, it has been found that the lifeof the etching solutions in accordance herewith can be increased afterthe pH level reaches substantially about 12.5 by the addition of smallamounts of sulfuric acid and boric acid which lower the pH level down toabout 11 and restores the effectiveness of the bath. It is to beunderstood further that multi-etched patterns can be achieved, inaccordance herewith, merely by repeating the application of the processtaught herein to nickel-surfaced objects.

As purely illustrative of the enhanced results achieved in accordanceherewith, one may note the following examples in which a plurality ofclean steel panels were first nickel plated and then etched with thenovel nickel etching solution in accordance herewith. The resultsachieved were aesthetically attractive, etched nickel-plate panelshaving low reflective qualities for light-diffusing finishes. It is tobe understood, however, that these examples are being presented with theunderstanding that they are to have no limiting character on the broaddisclosure of the invention as generally set forth herein and asdirected to men skilled in the art.

EXAMPLE 1 A clean steel panel was electroplated in a bright nickel bathto a thickness of 0.001 inch, that is, approximately 20 minutes at 60a.s.f. (amperes per square foot). The panel was then immersed in anickel etching solution, in accordance herewith, containing 100 ml./l.ethylenediamine, 40 g./l. sodium sulfate and 2S g./l. p-nitrobenzoicacid with the solution having a pH of 11 and the temperature beingsubstantially about 60 C. The etching solution was then seeded withabout 5 g./l. nickel sulfate. The purpose of the seeding is to saturatethe solution with nickel ethylenediamine sulfate prior to etching panelsso as to avoid stripping of nickel from the work until saturation isreached. After about 5 minutes, the panel was covered with purpleneedle-like crystals. However, in order to insure a thorough etching,the panel was left in for an additional ten minutes. Thereafter, thepanel was taken out and rinsed in water and immersed in a 50%hydrochloric acid pickle for a period of time sufiicient to remove thecrystals from the panel. At this stage, the panel was removed from theacid pickle and rinsed and dried. The result was a nickel plated steelpanel having formed over the surface thereof a novel crystalline etchpattern having great eye-appeal and low reflectance for light diffusingapplications.

In order to provide information as to the results achieved by furtherpost plating after the etching process, in accordance herewith, thepattern on the panel was enhanced by flashing in bright nickel for twominutes at 60 a.s.f., as well known, followed by plating with chromiumfor 2.5 minutes at 150 a.s.f.

EXAMPLE 2 A 2-liter etching solution was prepared by admixing 1 liter ofwater, 200 ml. of 98% ethylenediamine, 50

grams of p-nitrobenzoic acid, and grams of sodium sulfate with thevolume being adjusted to 2 liters. The pH was tested electrometricallyat 11.0. In this example, old nickel-plate panels were used instead offreshly plated panels thus requiring preliminary cleaning procedures.The temperature was raised to 60 C. and 4" x 6" preplated nickel panelswere prepared by scrubbing with Ajax for 1 minute, cathodic cleaned for1 minute and immersed in HCl pickle for 30 seconds. These panels werethen immersed in the etching solution for 10 minutes and then washed,and the resulting crystal formation was dissolved by immersing thepanels in a 50% hydrochloric acid pickle for a time sufiicient todissolve the crystals. The resulting panels had disposed over the entiresurface thereof a satisfactory and eye-appealing etched pattern.

EXAMPLE 3 A 2-liter etching solution was prepared by admixing one literof water, 200 ml. of 98% ethylenediamine, 50 grams of mixed isomers ofo-, m-nitrobenzoic acid and 80 grams of sodium sulfate. The volume ofthe solution was adjusted to a two-liter volume. The pH was determinedelectrometrically to be 11.0. The temperature of the etching solutionwas raised to 60 C., and nickel plated panels were prepared in the samemanner as in Example 2 noted above. The prepared nickel plated panelswere immersed in the etching solution for 10 minutes during which timecrystals formed over the entire surface thereof. The panels were thenremoved from the etching solution and washed with water and immersed ina 50% hydrochloric acid pickle for a time suflicient to dissolve thecrystals. The panels were then removed from the pickle and washed withcold water and then hot water and dried. The resulting etched panels hadimparted over the surfaces thereof a clearly defined etched patternsubstantially similar to the pattern on the panels from Example 2 notedabove. The pattern was the same as the crystal formation originallyformed over the surface of the panels. However, the etching was not asclearly defined as on the panels etched from the solution of Example 2,indicating that p-nitrobenzoic acid is a more satisfactory oxidant forthe purposes of carrying out this invention than the nitrobenzoic acidisomers of this example.

Accordingly, and as will be apparent from the foregoing, there areprovided in accordance herewith, methods and compositions for impartingdecorative and/or nonreflective etching to nickel surfaces disposed on awide variety of objects of different configuration useful for aplurality of applications while still avoiding and/or causing anysubstantial change to the advantageous properties of the nickel surface,or to nickel plated surfaces for the purposes for which it was formed onthe surface of the articles in the first place. Further, because of therelative ease of operation in accordance herewith in which objects areimmersed in a liquid solution so as to easily impart etching to eventhose objects of intricate configuration and because the ingredientsused for formulating the compositions in accordance herewith arerelatively inexpensive, the objects produced in accordance herewith arehighly advantageous commercially, and even in mass productionoperations.

While the methods and compositions herein disclosed form preferredembodiments of this invention, this invention is not limited to thosespecific methods and compositions, and changes can be made thereinwithout departing from the scope of this invention which is defined inthe appended claims.

What is claimed is:

1. A composition for etching the surface of nickelplated objectsconsisting of an aqueous solution having disposed therein between about50-250 ml./l. of ethylenediamine, between about 10-145 g./l. of a sourceof sulfate ion selected from the group consisting of sodium sulfate, thealkali metal sulfates, the alkali metal bisulfates, sulfuric acid,ammonium sulfate and ammonium bisulfate and mixtures thereof, andbetween about 3 g./l. to the upper limit of solubility of a nickeloxidant selected from the group consisting of o-nitrobenzoic acid,m-nitrobenzoic acid, p-nitrobenzoic acid and mixtures thereof;nitrophenol, m-nitrophenol, p-nitrophenol, and mixtures thereof;nitroparalfins, sodium bromate, potassium bromate, sodium iodate,potassium iodate, sodium periodate, potassium perlodate, sodiumnitrobenzoate, sodium nitrophenolate, and ammonium persulfate, saidaqueous solution having a pH within the range of about 9-12.

2. A composition as claimed in claim 1 in which said pH is about 10.5.

3. A composition as claimed in claim 1 in which said ethylenediamine ispresent in the amount of about 100 ml./l.

4. A composition as claimed in claim 3 in which said source of sulfateion is sodium sulfate.

5. A composition as claimed in claim 4 in which said nickel oxidant isp-nitrobenzoic acid.

6. A composition as claimed in claim 4 in which said nickel oxidant ispotassium iodate.

7. A composition as claimed in claim 5 in which said pH is about 10.5.

8. A composition as claimed in claim 6 in which said pH is about 10.5.

9. A composition as claimed in claim 4 in which said sodium sulfate ispresent in the amount of about g./l.

10. A composition as claimed in claim 5 in which said p-nitrobenzoicacid is present in the amount of about 25 g./l.

11. A composition as claimed in claim 6 in which said potassium iodateis present in the amount of about 25 g./l.

References Cited UNITED STATES PATENTS 3,163,524 12/1964 Weisberg et al.119 3,365,401 1/1968 Saubestre et al. 156-18 3,351,556 11/1967 Tsourmas252l03 3,399,143 8/1968 Slominski 15618 CHARLES E. VAN HORN, PrimaryExaminer US. Cl. X.R. 25 2-79. 1

